A metal-insulator-insulator-metal (MIIM) diode includes two electrical insulators disposed between two types of metals. The materials are tailored such that responsive to application of a forward bias, a quantum well forms between the two insulators enabling high-energy quantum tunneling. As a result, when a voltage is applied to the top metal that exceeds its threshold, tunneling electrons are accelerated across the quantum well. Quantum tunneling is faster than charging a switch junction in an integrated circuit, partially because charge travels through the metal rather than slower speed materials such as silicon.
MIIM diodes can be broadly incorporated within circuits that use conventional CMOS manufacturing as well as other semiconductor and printed circuit technologies. The MIIM diode has a sharper forward current-to-voltage (I-V) curve than the metal-insulator-metal (MIM) diode and, thus, may be used as a tunneling device with very high-speed performance capability that is potentially compatible with many substrate technologies. Use of MIIM diodes may potentially reduce cost, size, and improve performance of high-speed memory devices.
However, the insulator materials used in MIIM diodes must be relatively thin compared to the de Broglie electron wavelength and, thus, conventional deposition processes may cause undesirable chemical intermixing at the interface of the metals and insulators. Moreover, for the MIIM to function as a diode, there must be a preferred tunneling direction that results in a sharp bend in the diode forward characteristic current-voltage (I-V) curve. As a result of the high electric fields at the contact periphery or interface current caused by electron traps at the metal-insulator interface, significant edge leakage may occur in MIIM diodes. Due to high leakage currents, MIIM diodes may generally exhibit poor rectifying behavior. Increased asymmetry and nonlinearity in the I-V performance as might be achieved through avoidance of the aforementioned chemical intermixing and edge leakage exhibited by select devices as exemplified by conventional MIIM diodes would result in better rectification performance of such devices.
In view of the above, there is a need in the art for select devices that may be scaled to smaller sizes while exhibiting an increased asymmetrical I-V curve and associated improved rectifying behavior, as well methods of forming such select devices.